scholarly journals Influence of rainfall spatial resolution on flash flood modelling

2009 ◽  
Vol 9 (2) ◽  
pp. 575-584 ◽  
Author(s):  
M. Sangati ◽  
M. Borga
Keyword(s):  
Flash Flood ◽  
Hydrologic Model ◽  
Space Time ◽  
River Network ◽  
Spatial Aggregation ◽  
Peak Discharge ◽  
Radar Rainfall ◽  
High Resolution Radar ◽  
Rainfall Volume ◽  
Flood Simulations

Abstract. High resolution radar rainfall fields and a distributed hydrologic model are used to evaluate the sensitivity of flash flood simulations to spatial aggregation of rainfall at catchment scales ranging from 10.5 km2 to 623 km2. The case study focuses on the extreme flash flood occurred on 29 August 2003 on the eastern Italian Alps. Four rainfall spatial resolutions are considered, with grid size equal to 1-, 4-, 8- and 16-km. The influence of rainfall spatial aggregation is examined by using the flow distance as a spatial coordinate, hence emphasising the role of river network in the averaging of space-time rainfall. Effects of rainfall spatial aggregation are quantified by using a dimensionless parameter, represented by the ratio of rainfall resolution (Lr) to the characteristic basin length (Lw), taken as the square root of the watershed area. Increasing the Lr/Lw parameter induces large errors on the simulated peak discharge, with values of the peak discharge error up to 0.33 for Lr/Lw equal to 1.0. An important error source related to spatial rainfall aggregation is the rainfall volume error caused by incorrectly smoothing the rainfall volume either inside or outside of of the watershed. It is found that for Lr/Lw 1.0, around 50% of the peak discharge error is due to the rainfall volume error. Remaining errors are due to both the distortion of the rainfall spatial distribution, measured with respect to the river network, and to the reduced spatial variability of the rainfield. Further investigations are required to isolate and examine the effect of river network geometry on the averaging of space-time rainfall at various aggregation lengths and on simulated peak discharges.

scholarly journals Extending the Predictability of Hydrometeorological Flood Events Using Radar Rainfall Nowcasting

2006 ◽  
Vol 7 (4) ◽  
pp. 660-677 ◽  
Author(s):  
Enrique R. Vivoni ◽  
Dara Entekhabi ◽  
Rafael L. Bras ◽  
Valeriy Y. Ivanov ◽  
Matthew P. Van Horne ◽  
...  
Keyword(s):  
Lead Time ◽  
Flash Flood ◽  
Spatial Scales ◽  
Surface Characteristics ◽  
Hydrologic Model ◽  
Flood Events ◽  
Catchment Scale ◽  
Radar Rainfall ◽  
Time Operation ◽  
Forecast Lead Time

Abstract The predictability of hydrometeorological flood events is investigated through the combined use of radar nowcasting and distributed hydrologic modeling. Nowcasting of radar-derived rainfall fields can extend the lead time for issuing flood and flash flood forecasts based on a physically based hydrologic model that explicitly accounts for spatial variations in topography, surface characteristics, and meteorological forcing. Through comparisons to discharge observations at multiple gauges (at the basin outlet and interior points), flood predictability is assessed as a function of forecast lead time, catchment scale, and rainfall spatial variability in a simulated real-time operation. The forecast experiments are carried out at temporal and spatial scales relevant for operational hydrologic forecasting. Two modes for temporal coupling of the radar nowcasting and distributed hydrologic models (interpolation and extended-lead forecasting) are proposed and evaluated for flood events within a set of nested basins in Oklahoma. Comparisons of the radar-based forecasts to persistence show the advantages of utilizing radar nowcasting for predicting near-future rainfall during flood event evolution.

scholarly journals Effect of radar rainfall time resolution on the predictive capability of a distributed hydrologic model

2011 ◽  
Vol 15 (12) ◽  
pp. 3809-3827 ◽  
Author(s):  
A. Atencia ◽  
L. Mediero ◽  
M. C. Llasat ◽  
L. Garrote
Keyword(s):  
Sensitivity Analysis ◽  
Time Resolution ◽  
Heavy Rainfall ◽  
Flash Flood ◽  
Probabilistic Approach ◽  
Great Influence ◽  
Hydrologic Model ◽  
Radar Rainfall ◽  
Distributed Hydrologic Model ◽  
Correction Technique

Abstract. The performance of a hydrologic model depends on the rainfall input data, both spatially and temporally. As the spatial distribution of rainfall exerts a great influence on both runoff volumes and peak flows, the use of a distributed hydrologic model can improve the results in the case of convective rainfall in a basin where the storm area is smaller than the basin area. The aim of this study was to perform a sensitivity analysis of the rainfall time resolution on the results of a distributed hydrologic model in a flash-flood prone basin. Within such a catchment, floods are produced by heavy rainfall events with a large convective component. A second objective of the current paper is the proposal of a methodology that improves the radar rainfall estimation at a higher spatial and temporal resolution. Composite radar data from a network of three C-band radars with 6-min temporal and 2 × 2 km2 spatial resolution were used to feed the RIBS distributed hydrological model. A modification of the Window Probability Matching Method (gauge-adjustment method) was applied to four cases of heavy rainfall to improve the observed rainfall sub-estimation by computing new Z/R relationships for both convective and stratiform reflectivities. An advection correction technique based on the cross-correlation between two consecutive images was introduced to obtain several time resolutions from 1 min to 30 min. The RIBS hydrologic model was calibrated using a probabilistic approach based on a multiobjective methodology for each time resolution. A sensitivity analysis of rainfall time resolution was conducted to find the resolution that best represents the hydrological basin behaviour.

scholarly journals Error Propagation of Radar Rainfall Nowcasting Fields through a Fully Distributed Flood Forecasting Model

2007 ◽  
Vol 46 (6) ◽  
pp. 932-940 ◽  
Author(s):  
Enrique R. Vivoni ◽  
Dara Entekhabi ◽  
Ross N. Hoffman
Keyword(s):  
Error Propagation ◽  
Lead Time ◽  
Hydrologic Model ◽  
Forecast Errors ◽  
Flood Forecast ◽  
Spatiotemporal Resolution ◽  
Radar Rainfall ◽  
Forecast Lead Time ◽  
Flood Simulations ◽  
Storm Characteristics

Abstract This study presents a first attempt to address the propagation of radar rainfall nowcasting errors to flood forecasts in the context of distributed hydrological simulations over a range of catchment sizes or scales. Rainfall forecasts with high spatiotemporal resolution generated from observed radar fields are used as forcing to a fully distributed hydrologic model to issue flood forecasts in a set of nested subbasins. Radar nowcasting introduces errors into the rainfall field evolution that result from spatial and temporal changes of storm features that are not captured in the forecast algorithm. The accuracy of radar rainfall and flood forecasts relative to observed radar precipitation fields and calibrated flood simulations is assessed. The study quantifies how increases in nowcasting errors with lead time result in higher flood forecast errors at the basin outlet. For small, interior basins, rainfall forecast errors can be simultaneously amplified or dampened in different flood forecast locations depending on the forecast lead time and storm characteristics. Interior differences in error propagation are shown to be effectively averaged out for larger catchment scales.

Understanding the Scale Relationships of Uncertainty Propagation of Satellite Rainfall through a Distributed Hydrologic Model

2010 ◽  
Vol 11 (2) ◽  
pp. 520-532 ◽  
Author(s):  
Efthymios I. Nikolopoulos ◽  
Emmanouil N. Anagnostou ◽  
Faisal Hossain ◽  
Mekonnen Gebremichael ◽  
Marco Borga
Keyword(s):  
Error Propagation ◽  
Uncertainty Propagation ◽  
Hydrologic Model ◽  
Rainfall Runoff ◽  
Radar Rainfall ◽  
Flood Simulation ◽  
Small Watersheds ◽  
Actual Error ◽  
High Resolution Radar ◽  
Satellite Rainfall

Abstract The study presents a data-based numerical experiment performed to understand the scale relationships of the error propagation of satellite rainfall for flood evaluation applications in complex terrain basins. A satellite rainfall error model is devised to generate rainfall ensembles based on two satellite products with different retrieval accuracies and space–time resolutions. The generated ensembles are propagated through a distributed physics-based hydrologic model to simulate the rainfall–runoff processes at different basin scales. The resulted hydrographs are compared against the hydrograph obtained by using high-resolution radar rainfall as the “reference” rainfall input. The error propagation of rainfall to stream runoff is evaluated for a number of basin scales ranging between 100 and 1200 km2. The results from this study show that (i) use of satellite rainfall for flood simulation depends strongly on the scale of application (catchment area) and the satellite product resolution, (ii) different satellite products perform differently in terms of hydrologic error propagation, and (iii) the propagation of error depends on the basin size; for example, this study shows that small watersheds (<400 km2) exhibit a higher ability in dampening the error from rainfall to runoff than larger-sized watersheds, although the actual error increases as drainage area decreases.

scholarly journals Spatial moments of catchment rainfall: rainfall spatial organisation, basin morphology, and flood response

2011 ◽  
Vol 8 (3) ◽  
pp. 5811-5847 ◽  
Author(s):  
D. Zoccatelli ◽  
M. Borga ◽  
A. Viglione ◽  
G. B. Chirico ◽  
G. Blöschl
Keyword(s):  
Rainfall Variability ◽  
Analytical Framework ◽  
Hydrologic Model ◽  
Space Time ◽  
Simple Relationship ◽  
Radar Rainfall ◽  
Essential Information ◽  
Spatial Moments ◽  
Flood Response ◽  
Basin Morphology

Abstract. This paper provides a general analytical framework for assessing the dependence existing between spatial rainfall organisation, basin morphology and runoff response. The analytical framework builds upon a set of spatial rainfall statistics (termed "spatial moments of catchment rainfall") which describe the spatial rainfall organisation in terms of concentration and dispersion statistics as a function of the distance measured along the flow routing coordinate. The introduction of these statistics permits derivation of a simple relationship for the quantification of storm velocity at the catchment scale. The paper illustrates the development of the analytical framework and explains the conceptual meaning of the statistics by means of application to five extreme flash floods occurred in various European regions in the period 2002–2007. High resolution radar rainfall fields and a distributed hydrologic model are employed to examine how effective are these statistics in describing the degree of spatial rainfall organisation which is important for runoff modelling. This is obtained by quantifying the effects of neglecting the spatial rainfall variability on flood modelling, with a focus on runoff timing. The size of the study catchments ranges between 36 to 982 km2. The analysis reported here shows that the spatial moments of catchment rainfall can be effectively employed to isolate and describe the features of rainfall spatial organization which have significant impact on runoff simulation. These statistics provide essential information on what space-time scales rainfall has to be monitored, given certain catchment and flood characteristics, and what are the effects of space-time aggregation on flood response modeling.

scholarly journals Integrated high-resolution dataset of high intensity Euro-Mediterranean flash floods

2018 ◽  
Author(s):  
William Amponsah ◽  
Pierre-Alain Ayral ◽  
Brice Boudevillain ◽  
Christophe Bouvier ◽  
Isabelle Braud ◽  
...  
Keyword(s):  
High Resolution ◽  
High Intensity ◽  
Flash Flood ◽  
Flash Floods ◽  
Space Time ◽  
Radar Rainfall ◽  
Catchment Areas ◽  
Flood Response ◽  
The Mediterranean ◽  
Resolution Dataset

Abstract. This paper describes an integrated, high-resolution dataset of hydro-meteorological variables (rainfall and discharge) concerning a number of high-intensity flash floods that occurred in Europe and in the Mediterranean region from 1991 to 2015. This type of dataset is rare in the scientific literature because flash floods are typically poorly observed hydrological extremes. Valuable features of the dataset (hereinafter referred to as EuroMedeFF database) include i) its coverage of varied hydro-climatic regions, ranging from Continental Europe through the Mediterranean to Arid climates, ii) the high space-time resolution radar-rainfall estimates, and iii) the dense spatial sampling of the flood response, by observed hydrographs and/or flood peak estimates from post-flood surveys. Flash floods included in the database are selected based on the limited upstream catchment areas (up to 3000 km2), the limited storm durations (up to 2 days), and the unit peak flood magnitude. The EuroMedeFF database comprises 49 events that occurred in France, Israel, Italy, Romania, Germany, and Slovenia, and constitutes a sample of rainfall and flood discharge extremes in different climates. The dataset may be of help to hydrologists as well as other scientific communities because it offers benchmark data for the identification and analysis of the hydro-meteorological causative processes, evaluation of flash flood hydrological models and for hydro-meteorological forecast systems. The dataset also provides a template for the analysis of the space-time variability of flash flood-triggered rainfall fields and of the effects of their estimation on the flood response modelling. The dataset is made available to the public as a "public dataset" with the following DOI: (https://doi.org/10.6096/mistrals-hymex.1493).

scholarly journals Integrated high-resolution dataset of high-intensity European and Mediterranean flash floods

2018 ◽  
Vol 10 (4) ◽  
pp. 1783-1794 ◽  
Author(s):  
William Amponsah ◽  
Pierre-Alain Ayral ◽  
Brice Boudevillain ◽  
Christophe Bouvier ◽  
Isabelle Braud ◽  
...  
Keyword(s):  
High Resolution ◽  
High Intensity ◽  
Flash Flood ◽  
Flash Floods ◽  
Space Time ◽  
Radar Rainfall ◽  
Catchment Areas ◽  
Flood Response ◽  
The Mediterranean ◽  
Resolution Dataset

Abstract. This paper describes an integrated, high-resolution dataset of hydro-meteorological variables (rainfall and discharge) concerning a number of high-intensity flash floods that occurred in Europe and in the Mediterranean region from 1991 to 2015. This type of dataset is rare in the scientific literature because flash floods are typically poorly observed hydrological extremes. Valuable features of the dataset (hereinafter referred to as the EuroMedeFF database) include (i) its coverage of varied hydro-climatic regions, ranging from Continental Europe through the Mediterranean to Arid climates, (ii) the high space–time resolution radar rainfall estimates, and (iii) the dense spatial sampling of the flood response, by observed hydrographs and/or flood peak estimates from post-flood surveys. Flash floods included in the database are selected based on the limited upstream catchment areas (up to 3000 km2), the limited storm durations (up to 2 days), and the unit peak flood magnitude. The EuroMedeFF database comprises 49 events that occurred in France, Israel, Italy, Romania, Germany and Slovenia, and constitutes a sample of rainfall and flood discharge extremes in different climates. The dataset may be of help to hydrologists as well as other scientific communities because it offers benchmark data for the identification and analysis of the hydro-meteorological causative processes, evaluation of flash flood hydrological models and for hydro-meteorological forecast systems. The dataset also provides a template for the analysis of the space–time variability of flash flood triggering rainfall fields and of the effects of their estimation on the flood response modelling. The dataset is made available to the public with the following DOI: https://doi.org/10.6096/MISTRALS-HyMeX.1493.

scholarly journals Spatial moments of catchment rainfall: rainfall spatial organisation, basin morphology, and flood response

2011 ◽  
Vol 15 (12) ◽  
pp. 3767-3783 ◽  
Author(s):  
D. Zoccatelli ◽  
M. Borga ◽  
A. Viglione ◽  
G. B. Chirico ◽  
G. Blöschl
Keyword(s):  
Spatial Organization ◽  
Rainfall Variability ◽  
Hydrologic Model ◽  
Space Time ◽  
Simple Relationship ◽  
Catchment Scale ◽  
Radar Rainfall ◽  
Spatial Moments ◽  
Flood Response ◽  
Basin Morphology

Abstract. This paper describes a set of spatial rainfall statistics (termed "spatial moments of catchment rainfall") quantifying the dependence existing between spatial rainfall organisation, basin morphology and runoff response. These statistics describe the spatial rainfall organisation in terms of concentration and dispersion statistics as a function of the distance measured along the flow routing coordinate. The introduction of these statistics permits derivation of a simple relationship for the quantification of catchment-scale storm velocity. The concept of the catchment-scale storm velocity takes into account the role of relative catchment orientation and morphology with respect to storm motion and kinematics. The paper illustrates the derivation of the statistics from an analytical framework recently proposed in literature and explains the conceptual meaning of the statistics by applying them to five extreme flash floods occurred in various European regions in the period 2002–2007. High resolution radar rainfall fields and a distributed hydrologic model are employed to examine how effective are these statistics in describing the degree of spatial rainfall organisation which is important for runoff modelling. This is obtained by quantifying the effects of neglecting the spatial rainfall variability on flood modelling, with a focus on runoff timing. The size of the study catchments ranges between 36 to 982 km2. The analysis reported here shows that the spatial moments of catchment rainfall can be effectively employed to isolate and describe the features of rainfall spatial organization which have significant impact on runoff simulation. These statistics provide useful information on what space-time scales rainfall has to be monitored, given certain catchment and flood characteristics, and what are the effects of space-time aggregation on flood response modeling.

The Use of an Automated Nowcasting System to Forecast Flash Floods in an Urban Watershed

2006 ◽  
Vol 7 (1) ◽  
pp. 190-202 ◽  
Author(s):  
Hatim O. Sharif ◽  
David Yates ◽  
Rita Roberts ◽  
Cynthia Mueller
Keyword(s):  
High Resolution ◽  
Hydrologic Modeling ◽  
Flash Flood ◽  
Flash Floods ◽  
Hydrologic Model ◽  
Peak Discharge ◽  
Urban Settings ◽  
Flood Warning ◽  
Distributed Hydrologic Modeling ◽  
Physically Based

Abstract Flash flooding represents a significant hazard to human safety and a threat to property. Simulation and prediction of floods in complex urban settings requires high-resolution precipitation estimates and distributed hydrologic modeling. The need for reliable flash flood forecasting has increased in recent years, especially in urban communities, because of the high costs associated with flood occurrences. Several storm nowcast systems use radar to provide quantitative precipitation forecasts that can potentially afford great benefits to flood warning and short-term forecasting in urban settings. In this paper, the potential benefits of high-resolution weather radar data, physically based distributed hydrologic modeling, and quantitative precipitation nowcasting for urban hydrology and flash flood prediction were demonstrated by forcing a physically based distributed hydrologic model with precipitation forecasts made by a convective storm nowcast system to predict flash floods in a small, highly urbanized catchment in Denver, Colorado. Two rainfall events on 5 and 8 July 2001 in the Harvard Gulch watershed are presented that correspond to times during which the storm nowcast system was operated. Results clearly indicate that high-resolution radar-rainfall estimates and advanced nowcasting can potentially lead to improvements in flood warning and forecasting in urban watersheds, even for short-lived events on small catchments. At lead times of 70 min before the occurrence of peak discharge, forecast accuracies of approximately 17% in peak discharge and 10 min in peak timing were achieved for a 10 km2 highly urbanized catchment.

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